Monodisperse core–shell structured up-conversion Yb(OH)CO3@YbPO4:Er3+ hollow spheres as drug carriers

In this work, we report a facile solution-phase synthesis of monodisperse core-shell structured Yb(OH)CO₃@YbPO₄ hollow spheres (size around 380 nm) by utilizing the colloidal sphere of Yb(OH)CO₃ as the sacrificial template via the Kirkendall effect. The Er³+ doped Yb(OH)CO₃@YbPO₄ core-shell hollow spheres can be prepared similarly, which exhibit strong green emission under 980 nm NIR laser excitation even after loading with drug molecules. Most importantly, the sample can be used as an effective drug delivery carrier. The biocompatibility test on L929 fibroblast cells using MTT assay reveals low cytotoxicity of the system. A typical anticancer drug, doxorubicin hydrochloride (DOX), is used for drug loading, and the release properties, cytotoxicity, uptake behavior and therapeutic effects were examined. It is found that DOX is shuttled into cell by core-shell hollow spheres carrier and released inside cells after endocytosis, and the DOX-loaded spheres exhibited greater cytotoxicity than free DOX. These results indicate that the core-shell Er³+ doped Yb(OH)CO₃@YbPO₄ hollow spheres have potential for drug loading and delivery into cancer cells to induce cell death.